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SMD code 509J

Marking codes are not standardised, and the same code is reused by unrelated makers for unrelated parts. Below is every part in our tables printed with it, and any printed with a code that is easy to misread as it, from the manufacturers' own marking tables and published code lists.

509J is a capacitor marking

5 pF

5 pF capacitor, 5%

50 followed by the multiplier 9, in picofarads: 5 pF. Printed this way on film and larger ceramic capacitors; small chip ceramics are usually not printed at all. J is the tolerance, ±5%.

Check it with a meter

Lift one end and measure it on a capacitance range. A good one reads close to 5 pF. In circuit the meter also sees everything connected across it, so the reading means little until it is out. A failed one usually reads near 0 Ω, or a steady low resistance, on the ohms range, often from a crack. On the board a shorted capacitor shorts its whole rail. A failed reading does not change what to fit: the marking still says 5 pF.

On a transistor or diode body (SOT-23-6, SOT-23-5), 509J is a part code instead. Those parts are listed below.

3 parts are printed 509J

Not sure which one you have?

Answer up to 4 quick questions and these 3 parts are ranked, with a meter test that settles it. It works on a dead part too.

Load switch, all Global Mixed-mode Technology. What differs:

Is it dead? One meter test per kind

Parts of the same kind are tested the same way, so each test is here once. Each part above points to its own.

Load switch

Voltage, board powered, black probe on ground.

Working, it reads

Switched on, the output pin sits at the input voltage. Switched off, it sits near 0 V.

Dead, it reads

  • Output at the input voltage while switched off: the pass element has shorted.
  • Input present and switched on, no output: failed open, or shut down into a shorted load. Power off and measure output to ground.
On the board:
An output near 0 Ω to ground is usually the load. Lift the output pin to see which.
Compare:
If an identical part sits elsewhere on the board, measure it the same way: that is what this one should read.
Watch for:
The pinout and whether the enable is active high or low differ between parts. The datasheet gives both.

A dead part still carries its marking. A short or an open says it has failed, not that it is a different part.

Did you find your part?

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